| 摘要 |
PURPOSE:To make the polarity of a playback signal coincident and to improve the reliability of playback data by inverting the polarity of a recording signal on one surface when the recording signal is recorded on recording films of two surfaces which are initialized in the same direction previously. CONSTITUTION:A magnetic film 3 which has an easy magnetization axis perpen dicularly to the film surface is formed on a substrate to obtain a recording medium, which is irradiated with a laser beam 1 which is converged through an objective 2 to perform recording, reproduction, and erasure. When informa tion is recorded on and reproduced from this recording medium digitally by detecting intervals of recording marks or detecting the length and intervals of recording marks, the polarity of a recording signal SWB of digital data is made opposite in polarity on one recording surface B from a recording signal SWA on the outer surface A. Consequently between both surfaces A and B and playback signals SRA and SRB have the same polarity, so that the reliability by reproduction is improved.
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